In recent years, a display device whose display area is in a non-rectangular shape has been developed. In a case where every pixel is in a rectangular shape, when display control is performed pixel by pixel, the display sometimes has step-like ruggedness in an outermost circumference part of the display area in some cases. On the other hand, when using a black matrix or the like for covering non-display areas is attempted so as to smoothly display the outermost circumference part of the display area, however, the following occurs: in a pixel positioned on a boundary between the display area and the non-display area, subpixels that compose one pixel are covered partially, with the covered areas being different, respectively, which causes a problem that desired colors cannot be displayed.
As a technique to cope with such a problem, Patent Document 1 discloses a technique of forming pixels in non-rectangular shapes, thereby realizing a non-rectangular display area having a smooth outer-circumference contour without impairing brightness of images, visibility, and fidelity.